Sexual act with the female on top. The female does a split and inserts lubed penis into vagina. The male then grabs hold of the female's legs and spins her around rapidly, similar to that of a helicopter's blades.
Has a high failure rate, roughly 100%. Failure results in Female either falling over or vomiting, and Male losing penis.
Theoretically, a successful helicopter, if done fast enough, could generate lift for the female for about 2 seconds. There have been 3 reported cases of success, but they were all in Japan so you never know.

The helicopter is a very difficult (and awkward, don't forget awkward) but fulfilling sexual position. It is performed by the man who, while fully erect and inside the woman (... or whatever.), proceeds to turn his entire body in a circle around the woman. All the while turning his penis inside the woman's vagina (... or whatever.).

J.R.- The tricky part is making sure your member doesn't 'pop' out while you're doing this. ... And to keep from laughing. Otherwise its great.

When naked, a male moves up and down in a hula hoop motion, which causes the flacid penis to spin like a propellar. This act, although mainly done by children is also enjoyed by many men and their female audiences.

While the man is on top of a woman in a missionary type position, he lifts her legs which are extended, and moves them around at various 90 degree angles while doing her. The purpose is to have the man's penis feel big inside her and the movement of her legs will make her orgasm faster.